Combining these two meanings, we have the third, or philosophical sense of the word, which indicates that every organ is an individual existence, dependent more or less upon other organs for its maintenance and activity, yet biologically distinct. I do not mean that the heart will live independent of the body—at least, not for long, although it does continue to live and manifest its vital activity for some time after the animal’s death; and, in the cold-blooded animals, even after removal from the body. Nor do I mean that the legs of an animal will manifest vivacity after amputation; although even the legs of a man are not dead for some time after amputation; and the parts of some of the lower animals are often vigorously independent. Thus I have had the long tentacles of a _Terebella_ (a marine worm) living and wriggling for a whole week after amputation.[6] In speaking of the independence of an organ, I must be understood to mean a very dependent independence: because, strictly speaking, absolute independence is nowhere to be found; and, in the case of an organ, it is of course dependent on other organs for the securing, preparing, and distributing of its necessary nutriment. The tentacles of my _Terebella_ could find no nutriment, and they perished from the want of it, as the _Terebella_ itself would have perished under like circumstances. The frog’s heart now beating on our table with such regular systole and diastole, as if it were pumping the blood through the living animal, gradually uses up all its force; and since this force is not replaced, the beatings gradually cease. A current of electricity will awaken its activity, for a time; but, at last, every stimulus will fail to elicit a response. The heart will then be dead, and decomposition will begin. Dependent, therefore, every organ must be on some other organs. Let us see how it is also independent; and for this purpose we glance, as usual, at the simpler forms of Life to make the lesson easier. Here is a branch of coral, which you know to be in its living state a colony of polypes. Each of these multitudinous polypes is an individual, and each exactly resembles the other. But the whole colony has one nutritive fluid in common. They are all actively engaged in securing food, and the labours of each enrich all. It is animal Socialism of the purest kind—there are no rich and no poor, neither are there any idlers. Formerly, the coral-branch was regarded as one animal—an individual; and a tree was and is commonly regarded as one plant—an individual. But no zoologist now is unaware of the fact that each polype on the branch is a distinct individual, in spite of its connections with the rest; and philosophic botanists are agreed that the tree is a colony of individual plants—not one plant. [Illustration: Fig. 20. CAMPANULARIA (Magnified, and Natural Size).]